Livni thinks that she will get more votes by pandering to the secular anti-religious bloc, and is also motivated to ensure that Yair Lapid does not resurrect the Shinui party. However, it has been shown that that bloc is less than 20% of the population, and most of it voted for Livni in the past election. By such pandering, Livni is ensuring that religious parties (especially Shas) will not join her in a coalition. The reason that Livni (who got 28 seats as opposed to Likud's 27 seats) could not form a coalition in the past election is that she alienated Shas. And in almost every election in recent memory, the religious parties held the balance of power. In addition, Livni's anti-religious stance alienates many traditional non-religious voters, who while non-religious, still feel close to religion. There are many more of those voters than there are secular anti-religious voters.
Woman moderately wounded by firebomb thrown at her car in north J'lem (Haaretz)
from the article: Livni to Haaretz: Likud and Kadima must join forces for peace